Author(s): Rajendra Khanal; Sokly Siev; Sovanara Uk; Dillini Kodikara; Chihiro Yoshimura
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Keywords: Nutrient dynamics; Sediment dynamics; Eutrophication; Water level; Floodplain; Tonle sap lake
Abstract: The changes in water level of the lake directly affects the aquatic flora and fauna. Floodplain are formed when the land lateral to a river or lake are periodically inundated. In this presentation, we will share our ongoing research of understanding eutrophication in lake as a result of change in water level. The study site is Tonle Sap Lake (TSL), one of the largest freshwater lake in Southeast Asia, from where more than 36 samples of water at surface and 3 m depth and bottom sediment were analyzed for nutrients (esp. phosphorous) and sediment properties. Resuspension rates in open water near the shore were measured using a sediment trap. It was found that due to higher percentage (>80%) of fine particles in sediment greatly favored sediment resuspension during lower water level (1 m). The zero equilibrium phosphorus concentration, phosphorous concentration in solution where sorption equals to zero, of sediment in TSL was greater in resuspension condition (lower water level) then in non-disturbing (higher water level) condition implying in release of both the loosely bound and metal bound phosphorous from sediment to water. The higher resuspension rate was observed in the low water period, about 90% of gross sedimentation contributed from the resuspension. Sediment acted as the source of phosphorous in water during low water level and both as source and sink during high water level.
Year: 2018